Subject: [ietf-smtp] GreyList Retry Time Hints

From: Hector Santos <[email-masked]>
Date: Tue, 20 Jun 2017 23:06:46 -0400

My SMTP implementation has supported this draft specification for 
Greylisting:

https://tools.ietf.org/html/draft-santos-smtpgrey-02

The major improvement is leveraging the Retry Time hints provided by 
GreyListing Servers to reduce delivery delays. For examples:

   450 4.7.1. Greylist enabled. retry=00:02:00
   451 Temporary rejection. retry=00:00:30
   450 4.7.1. Temporary Greylist rejection. retry=01-00:10:00
   451 TempFail Retry=00:00:55
   421 Your connection is greylisted. Please try again later 
(retry=00:01:00)

Are there any other SMTP senders that have logic to extract this or 
any other retry time hints issued by Greylisting Servers for SMTP 
clients to requeue and reschedule an outbound mail retry time?

-- 
HLS